Anat

In an alternate 22nd century Earth, Anat was a guerrilla fighter and a member of the human resistance to the Daleks.

Anat led a group who travelled back to the 20th century to kill Sir Reginald Styles, who was believed to have been the cause of the wars that led to Dalek occupation.

After rescuing the Third Doctor and Jo Grant from the Daleks, she tried to convince them to help kill Styles and prevent their timeline from coming to pass. Instead, the Doctor deduced it was actually the guerrillas who had created their timeline in their attempt to prevent it. Anat allowed the Doctor and Jo to return to the 20th century and save the delegates, preventing the war from happening and altering the future.

Biography from the TARDIS Data Core article, licensed under CC-BY-SA